Advanced Information
WM8753L
OUTPUT SIGNAL PATH
The WM8753L output signal paths consist of digital filters, a stereo Hi-Fi DAC, Voice DAC, analogue
mixers and output drivers. The digital filters and DACs are enabled when the WM8753L is in
‘playback only’ or ‘record and playback’ mode. The mixers and output drivers can be separately
enabled by individual control bits (see Analogue Outputs). Thus it is possible to utilise the analogue
mixing and amplification provided by the WM8753L, irrespective of whether the DACs are running or
not.
The WM8753L Hi-Fi DAC receives digital input data on the DACDAT pin. The digital filter block
processes the data to provide the following functions:
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Digital volume control
Graphic equaliser and Dynamic Bass Boost
Sigma-Delta Modulation
Two high performance sigma-delta audio DACs convert the digital data into two analogue
signals (left and right).
The WM8753L Voice DAC receives digital input data on the VXDIN pin which is processed and up-
sampled by the digital filters and then sigma delta modulated to provide the analogue voice signal.
The analogue output from the stereo Hi-Fi DAC and the Voice DAC can then be mixed with each
other and the analogue signals from the analogue inputs. The mix is fed to the output drivers,
LOUT1/ROUT1, LOUT2/ROUT2, OUT3, OUT4, MONO1 and MONO2.
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LOUT1/ROUT1: can drive a 16Ω or 32Ω stereo headphone or stereo line output.
OUT3: can drive a 16Ω or 32Ω headphone or line output or buffered Vmid
LOUT2/ROUT2: can drive a 16Ω or 32Ω stereo headphone or stereo line output, or an 8Ω
mono speaker.
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MONO1 and MONO2: can drive a mono line output or other load down to 10kΩ
OUT4: can drive a 16Ω or 32Ω headphone or line output or buffered Vmid.
DIGITAL HI-FI DAC VOLUME CONTROL
The signal volume from each Hi-Fi DAC can be controlled digitally. The gain and attenuation range is
–127dB to 0dB in 0.5dB steps. The level of attenuation for an eight-bit code X is given by:
0.5 × (X-255) dB for 1 ≤ X ≤ 255;
MUTE for X = 0
The LDVU and RDVU control bits control the loading of digital volume control data. When LDVU or
RDVU are set to 0, the LDACVOL or RDACVOL control data is loaded into an intermediate register,
but the actual gain does not change. Both left and right gain settings are updated simultaneously
when either LDVU or RDVU are set to 1.
AI Rev 3.1 June 2004
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
